My invention pertains to cab signal control circuits for railroad interlockings. More specifically, this invention relates to control circuits for controlling the fail-safe application of cab signal energy to the several track sections within a railroad interlocking.
One goal of cab signal control systems for trains is to maintain a continuous signal or control condition, of whatever type is appropriate, on board the train as it passes through crossovers and other types of railroad interlockings. It is frequently difficult to provide cab signal energy in the rails fed toward an oncoming train in crossover layouts as the train wheel and axle units tend to shunt out the cab signal energy because of the complex track circuit connections necessary in order to maintain continuous train detection. In other words, because of the necessity of continuously detecting the train passing through the interlocking, dead spots are sometimes created in the cab signal energy supply. Otherwise, if circuit compromises are made, dead spots in the continuous detection of single cars within the interlocking may occur. An associated problem is the prevention of the failure of an insulated joint marking the limits of the interlocking from leaking improper cab signal energy to a train waiting outside the interlocking limits. A corresponding problem is to prevent supplying, to a train which may have inadvertently overrun an interlocking home signal, the cab signal energy intended for another train being routed through the interlocking or crossover location. Obviously, either one of these conditions can create an unsafe operating situation in the movement of the trains. Thus, special attention is paid to preventing such reception of improper cab signal energy by a train under these fault conditions.
Accordingly, an object of my invention is an improved cab signal control circuit arrangement for railroad interlockings.
Another object of the invention is cab signal circuits for railroad interlockings in which energy is transmitted to the train to control the signals only when a train occupies the associated track section within the interlocking.
Also an object of the invention is cab signal control circuits for railroad interlockings which prevent the supply of cab signal energy to a train halted outside the interlocking limits under any track circuit fault condition.
Still another object of my invention is a cab signal control circuit arrangement for a railroad interlocking which inhibits the transmission of cab signal energy through a faulty insulated joint at the interlocking limits by withholding the application of such energy until an authorized train occupies the corresponding track section.
A further object of the invention is control circuits for a railroad interlocking system which apply cab signal energy only as a train occupies each track section along its authorized route.
Another object of the invention is a cab signal energy network which inhibits the supply of such energy to a train inadvertently occupying an unauthorized route in a railroad interlocking.
A still further object of the invention is a control circuit network for a railroad interlocking which prevents a train inadvertently occupying the interlocking from receiving cab signal energy transmitted to a train following an authorized route.
A still further object of my invention is a control circuit network for a railroad interlocking which supplies cab signal energy to preset sections along an established route only as a train authorized to traverse that route successively occupies such sections in proper sequence.
Other objects, features, and advantages of my invention will become apparent from the following specification when taken in connection with the accompanying drawing and the appended claims.